Tuning Procedures and Temperament
Tuning consists of "setting the bearings" in an octave somewhere near middle C, and then appropriately "copying" this octave to all the other keys. You will need various harmonic tunings to set the bearings and only the middle string of each note in the "bearings octave" is initially tuned. The "copying" is performed by tuning in octaves. Once one string of each note is tuned in this way, the remaining string(s) of each note are tuned in unison.
In setting the bearings, we must choose which temperament to use. As explained in section 2 above, most pianos today are tuned to equal temperament (ET), but the historical temperaments (HsT) may be showing signs of gaining popularity, especially the Well temperaments (WT). Therefore, I have chosen ET and one WT, Kirnberger II (K-II), for this chapter. K-II is one of the easiest temperaments to tune; therefore, we will visit that first. Most people who are unfamiliar with the different temperaments may not notice any difference at first between ET and K-II; they will both sound terrific compared to a piano out of tune. Most pianists, on the other hand, should hear a distinct difference and be able to form an opinion or preference if certain pieces of music are played and the differences are pointed out to them. The easiest way to listen to the differences for the uninitiated is to use a modern electronic piano that has all these temperaments built into it, and to play the same piece, using each temperament. For an easy test piece, try Beethoven's Moonlight Sonata, 1st movement; for a more difficult piece, try the 3rd movement of his Waldstein Sonata. Also, try some of your favorite Chopin pieces. My suggestion is for a beginner to learn K-II first so that you can get started without too much difficulty, and then learn ET when you can tackle more difficult stuff. One drawback of this scheme is that you may like K-II so much over ET that you may never decide to learn ET. Once you get used to K-II, ET will sound a little lacking, or "muddy". However, you cannot really be considered a tuner unless you can tune ET. Also, there are many WT's that you may want to look into, that are superior to K-II in several respects.
WT tunings are desirable because they have perfect harmonies that are at the heart of music. However, they have one big disadvantage. Because the perfect harmonies are so beautiful, the dissonances in the “wolf” scales stand out and are very unpleasant. Not only that, but any string that is even slightly out of tune becomes immediately noticeable. Thus WT tunings will require much more frequent tunings than ET. You might think that a slight detuning of the unison strings in ET would be just as objectionable but, apparently, when the chords are as out of tune as they are in ET, the small unison detunings become less noticeable in ET. Therefore, for pianists who have sensitive ears to tuning, WT may be quite objectionable unless they can tune their own pianos. This is an important point because most pianists who can hear the advantages of WT are sensitive to tuning. The invention of the self-tuning piano may save the day for WT, because the piano will always be in tune. Thus WT may find wide acceptance only with electronic pianos and self-tuning pianos (when they become available - see section IV.6, “The Future of Piano”).
You can start tuning ET anywhere, but most tuners use the A440 fork to start, because orchestras generally tune to A440. The objective in K-II is to have C major and as many "nearby" scales as possible to be just (have perfect chords), so the tuning is started from middle C (C4 = 261.6, but most tuners will use a C523.3 tuning fork to tune middle C). Now, the A that results from K-II tuned from the correct C does not result in A440. Therefore, you will need two tuning forks (A and C) to be able to tune both ET and K-II. Alternatively, you can just start with only a C fork and start tuning ET from C. Having two tuning forks is an advantage because whether you start from C or from A, you can now check yourself when you get to the other one for ET.